Since a fingerprint, which is composed of a plurality of ridges in a stripe pattern, has two remarkable features that the fingerprint is invariable throughout life and the fingerprints of any two persons are different each other, the fingerprint has been used as a means to recognize a person from the old days.
According to the analysis of the fingerprint, an examiner compares two fingerprint data, and analyzes visually whether features on the fingerprint ridges match each other. Then, the examiner judges that two fingerprints are identical each other, in the case that number of the ridge features, which become paired out of two fingerprint data, becomes not smaller than a predetermined number.
Here, the ridge feature of the fingerprint means an end point or a bifurcation of a line which composes the stripe. The ridge features which become paired out of two data (in this case, fingerprint data) are called corresponding ridge features.
In many cases, not only the ridge feature such as the end point or the bifurcation but also other detailed features of the ridges, for example, a short line (dot) or a sweat pore are used for the judgment on identity. Accordingly, the ridge feature used for the judgment on the existence of difference between the fingerprints includes not only the end point or the bifurcation but also another detailed feature of the ridge.
In a trial, a document, which indicates a relation between authorized corresponding ridge features, is submitted together with two fingerprint photographs and two fingerprint gray images which are arranged adjacently. According to the trial in many countries, two fingerprints are judged to be identical each other in the case that about 12 corresponding ridge features are found out of the two fingerprint data. Details are described on 190 to 193 pages of non-patent document 1; “The Science of Fingerprints-Classification and Uses (John Edgar Hoover, US DOJ, FBI; 1963)”.
In recent years, a fingerprint matching system using a computer becomes prevailing, and consequently documentary evidence for the trial is also created by use of a computer in many cases. A function to edit and display two fingerprints so that the corresponding ridge features may be displayed clearly is called to be the Charting Function and is prevailing in USA in particular.
According to the Charting Function, two fingerprints are displayed adjacently, that is, one is arranged on the left side and the other is arranged on the right side so that the judgment on the existence of difference may be carried out easily. The display method mentioned above is called to be a side by side display. A figure and a screen which are displayed with the side by side display method are called to be a charting figure and a charting screen respectively. Two corresponding points are called to be charting points. A line, which ties two charting points, is also displayed in many cases. The line is called to be a charting line. The judgment on the existence of difference between the fingerprints is also called to be a fingerprint analysis.
The Charting Function, which is carried out semi-automatically by use of an automatic matching function, has been realized already. According to the semi-automatic Charting Function, it is unnecessary that the examiner inputs information on all corresponding ridge features by a manual operation. The ridge features, which become corresponding, are extracted by the automatic matching function, and then the corresponding ridge features are displayed automatically as the charting point. The examiner checks and modifies the corresponding ridge features which are displayed.
FIG. 10A and FIG. 10B show examples of the charting figures which are displayed by the charting function. FIG. 10A is the example of the charting figure to make a relation between the corresponding charting points clear through tying the charting points by the charting line and assigning the same number to the corresponding charting points. FIG. 10B is the example of display which is obtained through carrying out a linear transformation (rotation and parallel movement) for one image (right side fingerprint) of the fingerprint data of the charting figure shown in FIG. 10A so that the corresponding charting points are arranged almost horizontally.
Here, a technical document, which is applied before the present application, discloses a method to make the visual judgment on the existence of difference easy, for example, through modifying an image distortion so that one fingerprint image may match the other fingerprint image, and displaying two fingerprint images adjacently (for example, refer to patent document 1).
The patent document 1 mentioned above discloses a method to modify the image distortion on the basis of a distance between corresponding ridge features and a core of the fingerprint.
It is difficult to use the method mentioned above in the case that coordinates of the corresponding ridge features does not always match each other and there is no core of the fingerprint. The fingerprint with no core is, for example, an arched fingerprint or a latent fingerprint (partial fingerprint) whose core is not taken.
It is difficult to apply the modification method, which is disclosed in the above-mentioned patent document 1, to modification of the image of the above-mentioned fingerprint.
Patent document 2 discloses a method to support the analysis through modifying image distortion of one image out of two images perfectly by use of a large amount of corresponding points of the skeletons outputted as a result of skeleton matching, and overlapping the one image with the other image.
It is impossible to use the method in the case that coordinates of the corresponding ridge features do not always match each other, and the skeleton matching fails due to degraded quality of the image. Moreover, in the case that the method is applied to the latent fingerprint with low quality, the examiner must input skeleton data by a manual operation, and consequently, a work load of the examiner becomes severe.
Patent document 3 discloses an art to compare a plurality of images with ease through making a display means display simultaneously the images which photograph an eye in plural different states and include an identical photographing area.
Patent document 4 discloses an art which enables to compare simultaneously two different three-dimensional surface rendering images or the like, or to observe at once a state of three-dimensional distribution related to a plurality of different wall movement information.